This kind of damper has an input-side drive plate 61 in which a freely rotatable output-side driven plate 62 and liquid for producing a hysteresis torque are incorporated, and includes a damper mechanism for producing a torsional torque installed in between the driven plate 62 and the drive plate 61, as shown by FIG. 5 for example.
A projection edge 62a of the output-side driven plate 62 and a projection edge 66a of the input-side annular plate 66 compose a final stopper mechanism, and the input side is coupled integrally to the output side when the both edges contact each other at the maximum torsion angle.
In order to let free an impact torque etc., the annular plate 66 is designed to freely slidable relative to the drive plate 61 in a circumferential direction and is divided into two pieces by a plane perpendicular to its axis, and both side faces of the annular plate 66 are pressed onto the drive plate 61 with a specified pressure by means of urging springs 68, as illustrated by FIG. 4. By thus constructing the damper, a torque can be transmitted from the drive plate 61 to the annular plate 66, and a slip can be produced between the annular plate 66 and the drive plate 61 so as to release an excessive impact torque when this excessive impact torque is given.
Since liquid is filled in the drive plate 61, a coefficient of friction between friction surfaces 61b and 66b is small. Accordingly, when a torque limiter is designed to produce a torque by pressing flat friction surfaces each other, a very large pressing force is required for setting a specified limit torque value at which the slippage occurs. For this reason, a large number of springs 68 having a large spring force become necessary, and it is also required to widen the friction surfaces 61b and 66b, as shown by FIG. 5.